1. Field of the Invention
The present invention relates to image processing when reading an original image by a reading unit to which a plurality of sensor units are attached.
2. Description of the Related Art
There has been proposed an apparatus for reading an image on an original of a large size such as an A0 or A1 size by dividing it into a plurality of areas using a reading unit to which a plurality of sensor units are attached. There has also been proposed a technique of performing correction to ensure position consistency and correction to eliminate the discontinuity of tone or color when joining image data obtained by the plurality of sensor units.
Furthermore, there has been proposed a technique of correcting a tilt when an original is placed to be tilted with respect to a scanning direction assumed by a reading apparatus. For example, this technique detects the tilt angle of the original, and performs tilt correction processing according to the detected tilt angle.
In the case of a single sensor unit, even if there is an error in attachment of the sensor unit, it is possible to correct the attachment error using read image data. In the case of a plurality of sensor units, however, when considering the tilt or offset of the original placement, it is difficult to specify, using only image data, a sensor unit which has read a specific pixel. It is, therefore, impossible to correct an attachment error different for each sensor unit. A joint position on an original image changes for each reading operation due to the tilt or offset of the original placement, thereby making it difficult to perform the joint processing of image data.